Copolycarbonates form part of the group of the technical thermoplastics. They find a variety of uses in the electrical and electronics sector, as a housing material for lights, and in applications where exceptional thermal and mechanical properties are required, for example hairdryers, applications in the automotive sector, plastic covers, headlamp lenses or light guide elements, and also lamp covers or lamp bezels. These copolycarbonates can be used as a blending partner for further thermoplastic polymers.
In the case of these compositions, it is virtually always the case that good thermal and mechanical properties such as a high Vicat temperature (heat distortion resistance) and glass transition temperature are an absolute requirement.
As well as the good thermal and mechanical properties of polycarbonates, high transparency and low intrinsic yellowness (yellowness index, YI) are a further core property of polycarbonates. These good optical properties have to be maintained even over a prolonged period. This is particularly true of the thermal aging characteristics of components. In other words, the long-term performance under thermal stress of (co-)polycarbonates is a crucial quality criterion of great significance for the use of (co-)polycarbonate compositions for industrial components. If this criterion is not fulfilled, the (co-)polycarbonate composition and hence the component are subject to significant thermal yellowing, which is unwanted.
WO 2013/045552 discloses compositions comprising a copolycarbonate based on bisphenol A and 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane (bisphenol TMC).
EP 0 953 605 describes linear polycarbonate compositions having improved flow characteristics, characterized in that cyclic oligocarbonates are added in large amounts, for example 0.5% to 4%, and are homogenized by means of a twin-screw extruder in the matrix of a linear BPA polycarbonate at 285° C. In this case, flowability increases with increasing amount of cyclic oligocarbonates. However, this application says nothing about the thermal stability of corresponding polycarbonates.
EP 2 411 473 describes the use of polyacrylates containing imide structures for improvement of transmission.
WO 2009/056421 describes the use of polyethers which can likewise bring about an improvement. However, polyethers have too low an intrinsic thermal stability for use as blend partners in high-temperature polycarbonates.